Data compression (or coding) is the process of encoding a particular quantity of source information using fewer bits than are used for the un-encoded information. A wide variety of data compression techniques are known. A data compression technique may divide a given quantity of source data into portions and compress each portion individually. In image display systems, data compression techniques may be used to compress digital image data before storing or transmitting the data. Data compression is favored because the quantity of data to be stored or transmitted can be significantly reduced. When compressed data is fetched from memory or received from a transmitter, the data must be decompressed (or decoded) before it can be used. The process of decoding compressed data is generally the inverse of the coding process.
In some image display systems, image data may be compressed and stored in a memory as it is received, and read from memory and decompressed as it is needed by a display device, where the storing and reading functions are not synchronized.